The goals of the proposed program are to understand the chemical events constituting the maturation of ribosomal RNA, to define the characters of the enzymes which effect these maturation events, to determine the features of the polynucleotides which are recognized by such enzymes, and to pursue the biological rationale underlying postranscriptional cleavage. We shall use as a model system the maturation of 5S ribosomal RNA in Bacillus subtilis, which as we have shown, mimics in many respects the metabolism of the high molecular weight ribosomal RNA molecules. The program described will revolve about the following specific points: (1) Completion of analysis of the nucleotide sequences of the mature and precursor 5S ribosomal RNA molecules of Bacillus subtilis and a few other Bacillus species. (2) Further purification, identification, and study of the proteins involved in 5S rRNA maturation in B. subtilis and a search for enzymes involved in maturational cleavage of other rRNA molecules. (3) Determination of the structural features of the precursors of 5S rRNA which permit their recognition and specific cleavage by the enzyme involved. (4) Examination of the relative abilities of precursor and mature 5S rRNA molecules to associate specifically with ribosomal proteins. (5) Determination of the role of protein synthesis in maturation of 5S rRNA in B. subtilis. (6) Further exploration of the transcriptional organization of the genes specifying transfer RNA in prokaryotes. BIBLIOGRAPHIC REFERENCES: Marotta, C.A., F. Varricchio, I. Smith, S.M. Weissman, M.L. Sogin and N.R. Pace. The Primary Structure of Bacillus subtilis and Bacillus stearothermophilus 5S Ribonucleic Acids. J. Biol. Chem. 251: 3122-3127 (1976). Sogin, M.L., N.R. Pace, M. Rosenberg and S.M. Weissman. The Nucleotide Sequence of a 5S Ribosomal RNA Precursor from Bacillus subtilis. J. Biol. Chem. (in press, 1976).